Atrial fibrillation is the most common arrhythmia requiring treatment and is associated with significant morbidity and mortality. The ability to develop and prescribe new treatments for atrial fibrillation depends on the availability of better diagnostic tools that are simple and inexpensive enough to support their use for screening large numbers of patients. Recent evidence demonstrates that the electrophysiologic state of the atrium is a primary determinant of both the history of atrial fibrillation and its response to therapy. This provides a strong rationale for developing techniques for assessing atrial electrophysiology during fibrillation. The Creare team proposes to develop a noninvasive technique for assessing and classifying atrial fibrillation based on the surface electrocardiogram. This technique will assist clinicians in determining treatment strategies for patients suffering from atrial fibrillation. PROPOSED COMMERCIAL APPLICATION Creare's technique for noninvasive assessment of atrial fibrillation will provide the clinician with a powerful new tool for optimizing patient treatment. The technique is based on straightforward processing algorithms that can be readily incorporated into existing electrocardiogram systems.